A full length SSU rRNA-based workflow for high resolution monitoring of
nematode communities reveals direct and indirect responses to
plant-based manipulations
Abstract
Agricultural intensification has resulted in a decline of soil
biodiversity, and concerns about the deterioration of the biological
condition of soils prompted the development of measures to restore soil
life. Due to the overwhelming biodiversity of soils, evaluation of such
measures is not straightforward, and proxies are used to assess soil
health. Because of their trophic diversity, high abundance, and
relatively well-characterized ecologies, nematodes are often used as
soil health indicators. However, the scarcity of informative
morphological characters hampers the upscaling of this proxy. Here we
present a community analysis approach that uses nanopore sequencing to
generate full-length sequences of small subunit ribosomal DNAs (SSU
rDNA). Cover cropping is a common agricultural practice that stimulates
soil life, and we mapped the effects of ten cover crop treatments on
nematode communities in a field experiment. These analyses included the
monitoring of a high impact plant-parasite, Meloidogyne chitwoodi. In
total 132 nematode samples were analysed, and 65 nematode taxa were
detected, mostly at species level, including representatives of all
trophic groups. As a validation, all samples were analysed
microscopically for M. chitwoodi, and comparison of count and DNA read
data revealed highly similar results. Treatments did not only affect
plant-parasitic nematodes, but also free-living nematodes in a cover
crop-specific manner. Free-living nematodes from the same trophic group,
and even congeneric species, responded differentially to plant-mediated
manipulations of the soil microbiome. Hence, nanopore-based SSU rDNA
sequencing could facilitate a substantial refinement of the use of
nematodes as indicators for soil health.